I was trying to convert the Sentinel-2 1C product to radiance and came across two links first once says

```
radiance = ((pixelValueBandX * cos(incidenceAngle) * solarIrradianceBandX) / (pi * d2)) / 10000
where d2 is 1.0/U
```

Where as second one says

```
rad = rho * cos(radians(sza)) * Es * sc / (pi * d2)
where: d2 = 1.0 / U
scale: 1 / (0.001 * 1000) = 1 (default)
```

So, I have few questions amongst the two which one is correct. I don’t see any scaling factor in the first one. Moreover, does the incidence angle here denotes the value of **Mean_Sun_Angle.ZENITH_ANGLE** from file **MTD_TL.xml** ?

Also, Let’s say i do atmospheric correction using SEN2COR or DOS. I would get the BOA reflectance, right? So, then how do i convert it to a BOA radiance?